1. Field of the Invention
The invention concerns a single-use injector nozzle for machines for filling with biological products tubes usually called straws in the form of tubular sections of polymer material with a diameter of a few millimeters provided internally near one end with a composite stopper comprising, between two porous plugs, a volume of powder which gelifies in contact with an aqueous liquid, filling being effected by gripping the straws between two nozzles fitted with seals bearing on the ends, namely a suction nozzle connected to a vacuum pump and bearing on the end of the straw near the composite stopper and the injector nozzle fitted with a flexible tube which dips into a flask containing the biological product, the injector nozzle comprising a rigid tube referred to hereinafter as a needle adapted to be inserted into the straw and crimped axially in a body which has two external reference surfaces for respectively centering and longitudinally positioning the nozzle relative to a nozzle support.
2. Description of the Prior Art
The tubes known as straws referred to above have been extensively described in the art since the document FR-A-995 878 of 20 Sep. 1949. Their use has expanded considerably since that time, in parallel with the growth in artificial insemination of animals, especially cattle.
The present description will make particular reference to the insemination of cattle, which has been widely adapted since it was first introduced and may be regarded as typical, although artificial insemination is practised on horses, sheep, pigs, rabbits, poultry and in fish farming (this list is not exhaustive).
There are two fundamental requirements in respect of filling the straws: a) it must be carried out under the aseptic conditions that are the norm in veterinary practise and which enable certain identification of the donor animal, and b) the operations must be suited to large-scale use. In the latter regard, to give a clear idea of the orders of magnitude involved, one dose of bull semen fills approximately 800 straws and an artificial insemination center can process up to 60 bulls each day.
There is no need to dwell upon the process of collecting, checking the quality of and diluting the sperm: note that the receptacle or flask in which the sperm is collected contains sufficient to fill a batch of straws (up to 800 of them), which have an individual capacity of around 0.5 cm.sup.3.
The process of filling the straws by sucking dilute sperm through the flexible tube, the injector nozzle and the straw body by depressurizing the system through the suction nozzle and the composite stopper is outlined above. The composite stopper remains permeable to air while the powder contained between the two porous plugs has not gelified through contact with an aqueous liquid, in the present instance the liquid with which the sperm is diluted. When the straw is filled the composite stopper closes off the end of the straw.
On the machine the straws are placed in a hopper from which a dispenser inserts them into equi-distant calibrated notches on a conveyor belt with the straws perpendicular to the direction of movement of the belt. The belt is advanced stepwise by an amount representing one or three notches, depending on the required throughput. At a first workstation nozzles are disposed on supports which can move to and from transversely to the belt, the number of suction and injector nozzles being equal to the number of notches per stepwise movement of the belt. The supports move apart to release the straws and move towards each other to achieve sealed contact between the nozzles and the ends of the straws. The document FR-A-2 651 793 provides pertinent information on this filling process.
Note that at present the highest performing machines can achieve a rate of 72 cycles per minute with three straws filled simultaneously in each cycle, i.e. 216 straws/minute.
At a second workstation on the output side of the first end of each straw opposite the composite stopper is closed by crushing and welding it ultrasonically between an anvil and an ultrasound generator.
Note that reliable execution of the weld requires that over at least the length to be welded the straw does not contain any liquid. For this reason the injector needle must be long enough for the aspirated liquid to leave the needle and come into contact with the wall of the straw beyond the area to be welded. As the outside diameter of the needle is only slightly less than the inside diameter of the straw, it will be understood that the needle must be accurately coaxial with the straw, that the travel over which the nozzle supports move towards each other must be accurately controlled for the nozzles to be sealed to the ends of the straw without loading the straw in buckling mode which is hazardous to its integrity, and that all this must be achieved at the required rates of throughput.
The accuracy required has led the man skilled in the art to design the nozzles as precision mechanical components with a needle crimped rigidly into a metal body which has two reference surfaces for fitting it into the nozzle support, namely an axial centering surface, usually a cylindrical bearing surface, and a longitudinal positioning surface, usually a flat edge machined straight where the cylindrical bearing surface and a front holding part meet. The seal is provided by a cylindrical elastomer plug with a central hole through which the needle slides, being a snug fit, the plug abutting the forward edge of the body.
The suction nozzles do not represent any problem; the needle can be short; what is more, the suction nozzles do not come into contact with aseptic parts of the straw because of the isolation provided by the composite stopper; being at a lower pressure than the straw, there is no risk that they will inject pollutants into the straw. Simple daily maintenance and thorough weekly cleaning are sufficient.
The situation is totally different in respect of the injector nozzles, however. These, together with their flexible tube, must be strictly clean and dry on starting to fill straws with the sperm of a given donor animal and must be removed when all of the semen has been used and replaced with sterile nozzles for filling a new batch of straws with sperm from another donor.
To return to the previous example and to give an idea of the orders of magnitude involved, with 60 bulls per day and three injector nozzles per machine, no less than 180 nozzles are used each day. After use the flexible tubes are pulled off the nozzle spigots and discarded. The nozzles are placed in alcohol. At the end of each day the nozzles are carefully cleaned, fitted with new flexible tubes and sterilized for re-use the following day. This presupposes a large rotating stock of injector nozzles and time-consuming operations which must be carefully checked and still represent a risk of a nozzle containing traces of sperm from a previous animal.
In fact the operations involved in the daily preparation of the injector nozzles account for practically as much labor time as the filling operations themselves.
For a long time it has been realized that it would be beneficial to have injector nozzles fitted with a flexible tube to be dipped into the flask of semen that could be discarded after a single-use, that is to say after filling a batch of straws with dilute sperm from a single donor.
However, the mechanical precision required of the nozzles, as explained above, indicated a prohibitive unit cost, so that users have deemed it more cost-effective to continue in their previous ways than to discard the used nozzles.
With considerable experience in this art, we have undertaken to review all aspects of the problem of single-use injector nozzles.